Semiconductor device and method of manufacturing the same

ABSTRACT

A semiconductor device includes a semiconductor substrate having a main surface; a first coil formed on the main surface; a first insulating film formed over the first coil and having a first main surface; a second insulating film formed on the first main surface of the first insulating film and having a second main surface; and a second coil formed on the second main surface of the second insulating film, wherein the first main surface of the first insulating film has a first area on which the second insulating film is formed, and has a second area without the first area in a plan view, and wherein the second insulating film is surrounded with the second area in the plane view.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a Continuation application of U.S. patentapplication Ser. No. 14/625,390 filed on Feb. 18, 2015, which is aContinuation application of U.S. patent application Ser. No. 14/106,569,filed on Dec. 13, 2013, now U.S. Pat. No. 8,987,861 B2, issued on Mar.24, 2015, which is based on Japanese Patent Application No. 2012-279843filed on Dec. 21, 2012, the entire contents of which are herebyincorporated by reference.

BACKGROUND

The present invention relates to a semiconductor device and a method ofmanufacturing the same, and, for example, relates to an effectivetechnique applied to a semiconductor device having an inductor (coil)and a method of manufacturing a semiconductor device having an inductor.

A device that transfers electrical signals between two circuits thepotentials of inputted electrical signals of which are different fromeach other can be a device using a photocoupler. The photocoupler has alight-emitting element, such as a light-emitting diode, and alight-receiving element, such as a phototransistor, and uses thelight-emitting element to convert an inputted electrical signal intolight and uses the light-receiving element to restore the electricalsignal from the light, thereby transferring the electrical signal.

In addition, a technique of inductively coupling two inductors totransfer an electrical signal has been developed. For example, PatentDocument 1 (Japanese Patent Application Laid-Open Publication No.2009-302418) explained below discloses a circuit device including afirst inductor (200), a first insulating layer (100), and a secondinductor (300) (see FIG. 1). The first inductor (200) is positioned onone face of the first insulating layer (100), and the second inductor(300) is positioned on the other face of the first insulating layer(100), and positioned in a region where the second inductor (300) issuperposed on the first inductor (200), as viewed perpendicularly to theone face of the first insulating layer (100). In addition, as the firstinsulating layer (100), polyimide resin has been exemplified.

Incidentally, in the above paragraph, numerals in parentheses arereference numerals or figure numbers provided in the Patent Document 1.

SUMMARY

As a technique of transferring electrical signals between two circuitsthe inputted electrical signals of which have different potentials,there is a technique using the “photocoupler” mentioned above. However,since the photocoupler has the light-emitting element and thelight-receiving element, it is difficult to miniaturize thephotocoupler. Further, adoption of the photocoupler is limited because,for example, the photocoupler cannot follow an electrical signal whenthe frequency of the electrical signal is high.

On the other hand, in a semiconductor device inductively coupling twoinductors to transfer an electrical signal, the inductors can be formedby means of a microfabrication technique for a semiconductor device, andminiaturization of the device can be achieved. Further, the electricalcharacteristics of the semiconductor device are also good, and thus thedevelopment thereof is desired.

Especially, for further improvement in device characteristics such asimprovement in withstand voltage, examinations are required inconsideration of a device structure or a method of manufacturing thesame.

The above and other preferred aims and novel characteristics of thepresent invention will be apparent from the description of the presentspecification and the accompanying drawings.

The typical ones of the inventions disclosed in the present applicationwill be briefly described as follows.

A semiconductor device presented in an embodiment disclosed in thepresent patent application includes a laminated insulating film formedabove a first coil. This laminated insulating film includes a secondinsulating film, and a third insulating film formed on the secondinsulating film. The second insulating film and the third insulatingfilm is a laminated insulating film having a step formed by a mainsurface of the second insulating film and a main surface of the thirdinsulating film via side surfaces of the third insulating film, and asecond coil is formed on the laminated insulating film.

A method of manufacturing a semiconductor device presented in anembodiment disclosed in the present patent application includes a stepof forming a laminated insulating film above a first coil forming asecond insulating film on a first insulating film, and a step of forminga third insulating film on the second insulating film forming the thirdinsulating film so as to provide a step between the second insulatingfilm and the third insulating film. After the above-described steps, asecond coil is formed on the laminated insulating film.

A method of manufacturing a semiconductor device presented in anembodiment disclosed in the present patent application includes a stepof forming an active element in a first region of a semiconductorsubstrate, a step of forming a wiring in the first region of thesemiconductor substrate and forming a first coil in a second region ofthe semiconductor substrate, and a step of forming a laminatedinsulating film on a first insulating film on the first coil. The stepof forming a laminated insulating film includes a step of forming asecond insulating film on the first insulating film and a step offorming a third insulating film on the second insulating film formingthe third insulating film so as to provide a step between the secondinsulating film and the third insulating film. In addition, the methodof manufacturing a semiconductor device further includes a step offorming a second coil on the laminated insulating film and forming arewiring extended on the first insulating film from an opening portionof the first insulating film on the wiring.

According to a semiconductor device that is disclosed in the presentpatent application and that is described in an exemplified embodimentdescribed below, the characteristics of a semiconductor device can beimproved.

According to a method of manufacturing a semiconductor device that isdisclosed in the present patent application and that is described in anexemplified embodiment presented below, a semiconductor device havinggood characteristics can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view showing a configuration of a semiconductordevice of a first embodiment;

FIG. 2 is a sectional view showing the configuration of thesemiconductor device of the first embodiment;

FIG. 3 is a plan view showing an exemplary configuration of an inductorof the semiconductor device of the first embodiment;

FIG. 4 is a sectional view showing a manufacturing step of thesemiconductor device of the first embodiment;

FIG. 5 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 4;

FIG. 6 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 5;

FIG. 7 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 6;

FIG. 8 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 7;

FIG. 9 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 8;

FIG. 10 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 9;

FIG. 11 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 10;

FIG. 12 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 11;

FIG. 13 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 12;

FIG. 14 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 13;

FIG. 15 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 14;

FIG. 16 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 15;

FIG. 17 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 16;

FIG. 18 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 17;

FIG. 19 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 18;

FIG. 20 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 19;

FIG. 21 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 20;

FIG. 22 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 21;

FIG. 23 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 22;

FIG. 24 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 23;

FIG. 25 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 24;

FIG. 26 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 25;

FIG. 27 is a sectional view showing the manufacturing step of thesemiconductor device of the first embodiment, continued from FIG. 26;

FIG. 28 is a sectional view of an inductor portion of the semiconductordevice of the first embodiment;

FIG. 29 is a sectional view showing a configuration of a comparativeexample 1 of the first embodiment;

FIG. 30 is a sectional view showing a configuration of a comparativeexample 2 of the first embodiment;

FIG. 31 is a sectional view schematically showing that a laminated filmof polyimide films that is the comparative example 2 of the firstembodiment is in an inversely-tapered state;

FIG. 32 is a photograph of a laminated film of polyimide films in aninversely-tapered state;

FIG. 33 is a tracing of the shape of polyimide films in the photographof FIG. 32;

FIG. 34 is a block diagram showing a configuration of a semiconductordevice of a second embodiment;

FIG. 35 is a plan view showing the configuration of the semiconductordevice of the second embodiment;

FIG. 36 is a plan view schematically showing a configuration of asemiconductor device of a third embodiment;

FIG. 37 is a cross-sectional view schematically showing theconfiguration of the semiconductor device of the third embodiment;

FIG. 38 is a cross-sectional view schematically showing theconfiguration of the semiconductor device of the third embodiment;

FIG. 39 is a plan view schematically showing a configuration of asemiconductor device of a fourth embodiment;

FIG. 40 is a cross-sectional view schematically showing theconfiguration of the semiconductor device of the fourth embodiment;

FIG. 41 is a cross-sectional view schematically showing theconfiguration of the semiconductor device of the fourth embodiment;

FIG. 42 is a diagram showing a circuit diagram of a three-phase motor ina fifth embodiment.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

In the embodiments described below, the invention will be described in aplurality of sections or embodiments when required as a matter ofconvenience. However, these sections or embodiments are not irrelevantto each other unless otherwise stated, and the one relates to the entireor a part of the other as a modification example, details, or asupplementary explanation thereof. Also, in the embodiments describedbelow, when referring to the number of elements (including the number ofpieces, values, amount, range, and the like), the number of the elementsis not limited to a specific number unless otherwise stated or exceptthe case where the number is apparently limited to a specific number inprinciple. The number larger or smaller than the specified number isalso applicable.

Further, in the embodiments described below, it goes without saying thatthe components (including element steps) are not always indispensableunless otherwise stated or except the case where the components areapparently indispensable in principle. Similarly, in the embodimentsdescribed below, when the shape of the components, positional relationthereof, and the like are mentioned, the substantially approximate andsimilar shapes and the like are included therein unless otherwise statedor except the case where it is conceivable that they are apparentlyexcluded in principle. The same goes for the numerical value etc. (thenumber of pieces, values, amount, range, and the like) mentioned above.

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. Note that componentshaving the same function are denoted by the same reference symbolsthroughout the drawings for describing the embodiment, and therepetitive description thereof will be omitted. In addition, when thereare similar members (portions), a generic reference of the members maybe added with a symbol to denote an individual or specific portion. Inaddition, the description of the same or similar portions is notrepeated in principle unless particularly required in the followingembodiments.

Further, in some drawings used in the embodiments, hatching is used evenin a plan view so as to make the drawings easy to see.

Moreover, in a sectional view and a plan view, the dimensions of eachpart are not intended to correspond to those of an actual device, and,in order to make the drawings easy to understand, a specific part may berepresented in a relatively magnified manner. Also, even if a plan viewand a sectional view correspond to each other, the dimensions of eachpart may be differently represented.

First Embodiment Description of Structure

FIG. 1 is a conceptual illustration showing a configuration of asemiconductor device of a first embodiment. The semiconductor deviceshown in FIG. 1 is a semiconductor device having two chips (CH1, CH2)integrated in one package.

A chip (a semiconductor chip, a semiconductor piece) CH1 is mounted on adie pad DP1. The chip CH1 has a transformer composed of a lower-layerinductor (coil) Ia and an upper-layer inductor (coil) Ib. Theupper-layer inductor Ib is connected to a pad region PD2 in a chip CH2via a wire W. The lower-layer inductor Ia is connected to a peripheralcircuit PC via a wiring (not shown). In the peripheral circuit PC, alogic circuit composed of an element (active element), such as a MISFET,is formed. The peripheral circuit PC is connected via a wiring (notshown) to a pad region PD2 disposed at the end of the chip CH1. The padregion PD2 is connected via a wire W and an unshown lead to alow-voltage region LC having a circuit drivable at low voltage (forexample, 50 V or less).

The chip CH2 is mounted on a die pad DP2. The chip CH2 has a transformercomposed of a lower-layer inductor Ia and an upper-layer inductor Ib.The upper-layer inductor Ib is connected to a pad region PD2 in the chipCH1 via a wire W. The lower-layer inductor Ia is connected to aperipheral circuit PC via a wiring (not shown). In the peripheralcircuit PC, a logic circuit or the like composed of an element, such asa MISFET, is formed. The peripheral circuit PC is connected via a wiring(not shown) to a pad region PD2 disposed at the end of the chip CH2. Thepad region PD2 is connected via a wire W and a lead (not shown) to ahigh-voltage region HC having a circuit driven at high voltage (forexample, an AC RMS value of 100 Vrms or more).

For example, a transmission circuit in the peripheral circuit PC of thechip CH1 causes pulsed current to flow in the inductor Ia. At this time,the direction of the electric current caused to flow in the inductor Iais changed based on whether an electrical signal (a transmission signal,data) is “1” or “0”. This current of the inductor Ia produces inducedvoltage in the upper-layer inductor Ib. This voltage is transferred tothe chip CH2 via the wire W, amplified at a receiving circuit in theperipheral circuit PC of the chip CH2, and further, latched. In thismanner, the electrical signal can be wirelessly transferred by means ofmagnetic induction coupling. In other words, by connecting, via thetransformer, the low-voltage region LC and the high-voltage region HCwhich are electrically insulated from each other, an electrical signalcan be transferred between these regions (LC, HC).

In addition, by forming inductors (Ia, Ib) constituting a transformer inthe same manner as a wiring or the like by means of microfabrication forforming a semiconductor device, the peripheral circuits PC and theinductors (Ia, Ib) can be integrated and formed on the same chip.

The shape of a conductive pattern constituting the transformer, as shownin FIG. 1, can be a spiral conductive pattern (see FIG. 3).

FIG. 2 is a sectional view showing the configuration of thesemiconductor device of the first embodiment. The semiconductor deviceshown in FIG. 2 is a semiconductor device having a transformer, and, forexample, corresponds to a cross section taken along the line A-A in FIG.1.

The semiconductor device of the first embodiment is formed by utilizingan SOI (Silicon on Insulator) substrate, and has a peripheral circuitforming region 1A and a transformer forming region 2A.

An SOI substrate 1 has a supporting substrate 1 a, an insulating layer(a buried insulating layer, BOX) 1 b formed on the supporting substrate1 a, and a semiconductor layer (for example, a silicon layer 1 c) formedon the insulating layer 1 b.

In the peripheral circuit forming region 1A, a semiconductor element,such as a MISFET (Metal Insulator Semiconductor Field EffectTransistor), is formed. The MISFET constitutes the peripheral circuit PCshown in FIG. 1, for example. A MISFET is here exemplified as asemiconductor element, but, in addition to a MISFET, a capacitor, amemory element, a transistor having another configuration, or the likemay be formed in the peripheral circuit forming region 1A.

Further, an interlayer insulating film IL1 is formed on MISFETs (NT,PT), and first-layer wirings M1 are formed on the interlayer insulatingfilm IL1. The MISFETs (NP, PT) and the first-layer wirings M1 areconnected together via plugs P1. In addition, second-layer wirings M2are formed on the first-layer wirings M1 via an interlayer insulatingfilm IL2. The first-layer wirings M1 and the second-layer wirings M2 areconnected together via plugs (not shown) formed in the interlayerinsulating film IL2. In addition, third-layer wirings M3 are formed onthe second-layer wirings M2 via an interlayer insulating film IL3. Thesecond-layer wirings M2 and the third-layer wirings M3 are connectedtogether via plugs (not shown) formed in the interlayer insulating filmIL3. In the semiconductor device of the first embodiment, thethird-layer wirings M3 are uppermost-layer wirings. That is, by thewirings to the third-layer wirings M3, desired wire connection of thesemiconductor elements (for example, the above-described MISFET) isachieved, and desired operation can be performed. Therefore, forexample, pad regions PD1 that are exposed parts of the third-layerwirings (uppermost-layer wirings) can be utilized to perform a test(test step) to determine whether or not the semiconductor deviceperforms the desired operation.

Rewirings RW are formed on the third-layer wirings M3 via an interlayerinsulating film (an insulating film, a protective film) IL4. Theinterlayer insulating film IL4 is composed of a laminated film of aninsulating film IL4 a and an insulating film IL4 b on the insulatingfilm IL4 a. The rewirings RW are wiring that draws out, to desiredregions (pad regions PD2) of the chip, the pad region PD1 which is apart of the uppermost-layer wirings (here, the third-layer wirings M3).

A transformer having an inductor Ia and an inductor Ib is formed in thetransformer forming region 2A. The lower-layer inductor Ia is formed inthe same layer as the third-layer wirings M3. The inductor Ib is formedon the Inductor Ia via the interlayer insulting film IL4 and polyimidefilms PI1 and PI2. The polyimide films PI1 and PI2 are not formed in theperipheral circuit forming region 1A. That is, a step St1 is formedbetween the interlayer insulating film IL4 (insulating film IL4 b) andthe polyimide film PI1. Thus, a height difference corresponding to thefilm thickness of the polyimide films PI1 and PI2 (a laminated film, alaminated insulating film) exists between the forming position of theinductor Ia and the forming position of the rewiring RW, but theinductor Ia and the rewiring RW are formed of the same material (thesame step). In addition, the polyimide film PI2 is so formed as to beretreated from the end of the polyimide film PI1. In other words, thepolyimide films PI1 and PI2 are formed in a stairs-like shape (pyramidshape). That is, a step St2 is formed between the polyimide films PI1and PI2. The polyimide film is a polymer having a recurring unitcontaining an imide bond, and is a kind of organic insulating film.Other than the polyimide film, another organic insulating film, such asepoxy, PBO, acrylic, or WRP resins, can be used. Polyimide resins areorganic resins preferably used for a device requiring high resistance to200° C. or higher heat, and can be differently used based on thecoefficient of thermal expansion, mechanical strength, such asductility, or cure temperature of a material. In addition, a siliconoxide film or a silicon nitride film can be preferably used as inorganicinsulating films (IL1, IL2, IL3, IL4 a, etc.) used in the firstembodiment, but the inorganic insulating films are not limited to thesilicon oxide film and the silicon nitride film.

Since the laminated structure of the polyimide films PI1 and PI2 isadopted in this manner, the film thickness of an insulating film betweenthe inductors Ia, Ib can be increased. This can improve withstandvoltage between the inductors Ia, Ib.

Further, since the polyimide films PI1 and PI2 are so formed in astairs-like shape as to have the steps St1, St2, the film formability ofthe polyimide films PI1 and PI2 can be improved, so that peeling-off ofthe polyimide films PI1 and PI2 can be reduced.

A polyimide film PI3 is formed on the rewiring RW and the inductor Ia.The polyimide film PI3 is so formed as to be retreated from the end ofthe polyimide film PI2. In other words, in the transformer formingregion 2A, a step St3 is formed between the polyimide film PI2 and thepolyimide film PI3. In addition, the polyimide film PI3 in the borderbetween the peripheral circuit forming region 1A and the transformerforming region 2A is so removed that an opening portion (recess) OAthrough which at least the interlayer insulating film IL4 (insulatingfilm IL4 b) is exposed is formed.

Thus, since the rewiring RW is covered with the polyimide film PI3, therewiring RW can be protected. Further, since the inductor Ib is coveredwith the polyimide film PI3, the inductor Ib can be protected. Inaddition, since the polyimide film PI3 is so formed as to be retreatedfrom the end of the polyimide film PI2 such that a laminated film ofpolyimide films (PI1 to PI3) is formed in a stairs-like shape (pyramidshape) in the transformer forming region 2A, a creepage distance betweenthe pad region PD2 of the peripheral circuit forming region 1A and thepad region PD2 of the transformer forming region 2A can be increased, sothat withstand voltage can be improved (see FIG. 38 for a thirdembodiment, FIG. 41 for a fourth embodiment, etc.).

Regarding the configuration of the inductor, the shape thereof is notlimited as long as the inductor can generate a magnetic field whenelectric current flows, but it is preferred that a conductive film (aconducting film, a conductor film) having a spiral planar shape be used.FIG. 3 is a plan view showing a configuration example of an inductor ofthe semiconductor device of the first embodiment. The inductor shown inFIG. 3 corresponds to the upper-layer inductor Ib, for example. In FIG.3, the inductor is composed of a conductive film having a spiral planarshape as viewed from above, and two spiral conductive films are arrangedsymmetrically with respect to the center line of the pad region PD2located in the center in FIG. 3. Further, an inner end of the spiralconductive film located on the left side in FIG. 3 is connected to thepad region PD2 located in the center of the spiral. In addition, aninner end of the spiral conductive film located on the right side inFIG. 3 is connected to the pad region PD2 located in the center of thespiral. In the first embodiment, the set of conductive films includingthe pad regions PD2 is referred to as an inductor. Each pad region PD2is connected to a receiving circuit (Rx) of another chip, for example,by, a wire (W) or the like (see FIG. 34, FIG. 35, etc.)

The lower-layer inductor Ia is composed of a spiral conductive film,like the upper-layer inductor Ib, and, for example, can be formed in aspiral planar shape shown in FIG. 3 as viewed from above. An end (padregion) of the spiral conductive film is connected to a transmissioncircuit (Tx) via a wiring in a layer below the inductor Ia, for example(see FIG. 34, FIG. 35, etc.).

[Description of Manufacturing Method]

Next, with reference to FIGS. 4 to 27, a method of manufacturing thesemiconductor device of the first embodiment will be described, and theconfiguration of the semiconductor device will be made clearer. FIGS. 4to 27 are sectional views showing manufacturing steps of thesemiconductor device of the first embodiment.

As shown in FIG. 4, an SOI substrate, for example, is prepared as asemiconductor substrate. The SOI substrate 1 is composed of a supportingsubstrate 1 a composed of silicon single crystal (semiconductor film),an insulating layer (a buried insulating layer, BOX) 1 b formed on thesupporting substrate 1 a, and a silicon layer (a semiconductor layer, asemiconductor film, a thin-film semiconductor film, a thin-filmsemiconductor region) 1 c formed on the insulating layer 1 b. The SOIsubstrate 1 has a peripheral circuit forming region 1A and a transformerforming region 2A.

Next, a device isolation insulating film STI is formed in the siliconlayer 1 c of the SOI substrate 1. The device isolation insulating filmSTI is provided to prevent elements from interfering with each other.The device isolation region can be formed by means of an STI (shallowtrench isolation) process, for example.

For example, by means of a photolithography technique and an etchingtechnique, a device isolation trench is formed on the silicon layer 1 cof the SOI substrate 1. The photolithography technique is a technique toform a photoresist film (mask film) having a desired shape by forming aphotoresist film on a film to be etched (here, the silicon film 1 c) andexposing and developing the photoresist film. In addition, removing afilm to be etched (here, the silicon film 1 c) is referred to asetching, and here, since an underlayer film to be etched (here, thesilicon film 1 c) is removed using a photoresist film as a mask, thefilm to be etched can be selectively removed. Incidentally, after theetching step, the photoresist film is removed by an ashing process orthe like.

Next, a silicon oxide film is so deposited on the SOI substrate 1 by aCVD (Chemical Vapor Deposition) process or the like as to be thick justenough to fill in the device isolation trench, and the silicon oxidefilm outside the device isolation trench is removed by a chemicalmechanical polishing (CMP) process, an etching-back process, or thelike. Thus, the silicon oxide film can be buried in the device isolationtrench. The device isolation insulating film STI can also be formed bymeans of a LOCOS (Local Oxidation of Silicon) process.

Next, MISFETs (NT, PT) are formed in the peripheral circuit formingregion 1A. Although the method of forming the MISFETs is not limited,the MISFETs can be formed according to the following steps, for example.

First, a gate insulating film GOX is formed on the SOI substrate 1, andfurther a polycrystalline silicon film is formed on top of the gateinsulating film GOX. Although the method of forming the gate insulatingfilm GOX is not limited, the gate insulating film GOX is formed bythermally oxidizing the surface of the silicon layer 1 c, for example.In that case, the gate insulating film GOX is composed of a siliconoxide film. Other than the silicon oxide film, a silicon oxynitride filmmay be used as the gate insulating film GOX. A high-dielectric-constantfilm (so-called high-k film) can also be used as the gate insulatingfilm GOX. Further, a film forming process other than the thermaloxidation process, such as a CVD process, can also be used to form thegate insulating film GOX.

The polycrystalline silicon film on the gate insulating film GOX can beformed by means of a CVD process, for example. It should be noted thataccording to the characteristics of each MISFET (NT, PT), impurities maybe implanted in regions for forming gate electrodes GE. That is,impurities are implanted in a desired region in the polycrystallinesilicon film.

Next, the gate electrodes GE are formed by patterning thepolycrystalline silicon film by means of the photolithography techniqueand the etching technique. Next, source/drain regions SD having an LDDstructure are formed in the silicon layers 1 c on both sides of eachgate electrode GE.

First, an n⁻-type semiconductor region (low-concentration n-typeimpurity region) is formed by forming a photoresist film (not shown)having an opening portion in an n-channel type MISFET (NT) formingregion of the peripheral circuit forming region 1A, and thenion-implanting n-type impurities using the photoresist film and the gateelectrode GE as masks. Thereafter, the photoresist film is removed.

Next, a p⁻-type semiconductor region (low-concentration p-type impurityregion) is formed by forming a photoresist film (not shown) having anopening portion in a p-channel type MISFET (PT) of the peripheralcircuit forming region 1A, and then ion-implanting p-type impuritiesusing the photoresist film and the gate electrode GE as masks.Thereafter, the photoresist film is removed.

Next, a sidewall film SW is formed on each sidewall of the gateelectrodes GE by forming a silicon oxide film by a CVD process, forexample, as an insulating film on the SOI substrate 1, and thenanisotropically etching this silicon oxide film.

Next, an n⁺-type semiconductor region (high-concentration n-typeimpurity region) is formed by forming a photoresist film (not shown)having an opening portion in the n-channel type MISFET (NT) formingregion of the peripheral circuit forming region 1A, and thenion-implanting n-type impurities using the photoresist film, the gateelectrode GE, and the sidewall films SW as masks. Thereafter, thephotoresist film is removed.

Next, a p⁺-type semiconductor region (high-concentration p-type impurityregion) is formed by forming a photoresist film (not shown) having anopening portion in the p-channel type MISFET (PT) forming region of theperipheral circuit forming region 1A, and then ion-implanting p-typeimpurities using the photoresist film, the gate electrode GE, and thesidewall films SW as masks. Thereafter, the photoresist film is removed.Next, a thermal treatment (annealing) is performed to activate impurityions implanted at the previous steps.

According to the above steps, MISFETs (NT, PT) having the source/drainregion SD having an LDD structure having a high-concentration impurityregion and a low-concentration impurity region can be formed.

Next, as shown in FIG. 5, the interlayer insulating film IL1 is formedon the SOI substrate 1, including on the MISFETs (NT, PT). For example,after a silicon oxide film is deposited by a CVD process, the surface ofthe interlayer insulating film IL1 is planarized by means of a CMPprocess or the like, if necessary.

Next, contact holes are formed by patterning the interlayer insulatingfilm IL1. Next, plugs P1 are formed by burying a conductive film in thecontact holes. For example, a laminated film of a titanium film and atitanium nitride film is deposited on the interlayer insulating film IL1including the inside of the contact holes as a barrier film by asputtering process or the like. Next, on the barrier film, a tungsten(W) film as a main conductive film is so deposited by a CVD process orthe like as to be thick just enough to fill the contact holes. Next, thebarrier film and the main conductive film which are unnecessary on theinterlayer insulating film IL1 are removed by a CMP process. Thereby,the plugs P1 are formed.

Next, on the interlayer insulating film IL1 and the plugs P1, alaminated film is formed as a conductive film by sequentially depositinga titanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, first-layer wirings M1 are formed on theplugs P1 by patterning the laminated film by means of thephotolithography technique and the etching technique.

Next, as shown in FIG. 6, the interlayer insulating film IL2 composed ofa silicon oxide film is formed on the first-layer wirings M1 by a CVDprocess or the like. Next, contact holes (not shown) are formed on thefirst-layer wirings M1 by patterning the interlayer insulating film IL2.

Next, plugs (not shown) are formed in the interlayer insulating film IL2by burying a conductive film in the contact holes. These plugs can beformed in the same manner as the plugs P1.

Next, on the interlayer insulating film IL2 and the plugs, a laminatedfilm is formed as a conductive film by sequentially depositing atitanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, second-layer wirings M2 are formed on theplugs by patterning the laminated film by means of the photolithographytechnique and the etching technique.

Next, the interlayer insulating film IL3 composed of a silicon oxidefilm is formed on the second-layer wirings M2 by a CVD process or thelike. Next, contact holes (not shown) are formed on the second-layerwirings M2 by patterning the interlayer insulating film IL3.

Next, plugs (not shown) are formed in the interlayer insulating film IL3by burying a conductive film in the contact holes. These plugs can beformed in the same manner as the plugs P1.

Next, on the interlayer insulating film IL3 and the plugs, a laminatedfilm is formed as a conductive film by sequentially depositing atitanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, third-layer wirings M3 are formed on theplugs by patterning the laminated film by means of the photolithographytechnique and the etching technique.

Here, in the transformer forming region 2A, a lower-layer inductor Ia isformed in the same layer as the third-layer wirings M3. That is, at thetime of patterning the above laminated film, the above-described spiralconductive film (inductor Ia) is formed in the transformer formingregion 2A (see FIG. 3).

Of course, the second-layer wiring M2 (for example, a wiring thatelectrically connects the lower-layer inductor Ia and a peripheralcircuit) can also be formed in the transformer forming region 2A. Also,the first-layer wiring M1 can be formed in the transformer formingregion 2A.

Next, as shown in FIG. 7, an insulating film IL4 a is formed on thethird-layer wirings M3 (here, the uppermost layer wirings) and theinterlayer insulating film IL3. For example, the insulating film IL4 ais formed by depositing a silicon nitride film having a film thicknessof about 1 to 4 μm by a CVD process or the like.

Next, a photosensitive polyimide film, for example, is applied to theinsulating film IL4 a as an insulating film IL4 b. For example, thepolyimide film is formed by rotationally applying a polyimide precursorsolution to the surface of the SOI substrate 1, and then drying thesame. Next, as shown in FIG. 8, an opening portion (an opening region,an exposed portion of the third-layer wiring M3) is formed by removingthe polyimide film (IL4 b) in the pad region PD1 by exposing anddeveloping the photosensitive polyimide film (IL4 b). Thereafter, thepolyimide film (IL4 b) is cured by a thermal treatment. The filmthickness of the polyimide film (IL4 b) is about 3 to 10 for example.Next, the third-layer wiring M3 in the pad region PD1 is exposed byremoving the insulating film IL4 a by etching. Thus, the interlayerinsulating film IL4 having the opening portion in the pad region PD1 andcomposed of the laminated film of the insulating film IL4 a and theinsulating film IL4 b is formed.

Next, as shown in FIG. 9, a photosensitive polyimide film PI1 is appliedto the insulating film IL4 b including the pad region PD1 as a firstinsulating film (an interlayer insulating film, an insulating film forensuring withstand voltage, an insulating film between inductors). Forexample, the polyimide film PI1 is formed by rotationally applying apolyimide precursor solution to the surface of the SOI substrate 1, andthen drying the same. Next, as shown in FIG. 10, the polyimide film PI1in the peripheral circuit forming region 1A is removed by exposing anddeveloping the photosensitive polyimide film PI1. Thereafter, thepolyimide film PI1 is cured by a thermal treatment. The film thicknessof the polyimide film PI1 is about 3 to 10 μm, for example. Here, sincethe insulating film IL4 b extends from the transformer forming region 2Ato the peripheral circuit forming region 1A, the step St1 is formedbetween the insulating film IL4 b and the polyimide film PI1.

Next, as shown in FIG. 11, a photosensitive polyimide film PI2 isapplied on the insulating film IL4 b including the pad region PD1 andthe polyimide film PI1 as a second insulating film (an interlayerinsulating film, an insulating film for ensuring withstand voltage, aninsulating film between inductors). For example, the polyimide film PI2is formed by rotationally applying a polyimide precursor solution to thesurface of the SOI substrate 1, and then drying the same. Next, thepolyimide film PI2 in the peripheral circuit forming region 1A isremoved by exposing and developing the photosensitive polyimide filmPI2. At this time, the polyimide film PI2 is retreated from the end ofthe polyimide film PI1. Thus, the end of the polyimide film PI1 isexposed, and the step St2 is formed between the polyimide film PI1 andthe polyimide film PI2. Thereafter, the polyimide film PI2 is cured by athermal treatment. The film thickness of the polyimide film PI1 is about3 to 10 μm, for example. Further, the retreat amount of the polyimidefilm PI2, i.e., a distance between the end of the polyimide film PI1 andthe end of the polyimide film PI2 (step width) is 50 μm to 100 μm, forexample.

Since the polyimide films PI1 and PI2 are laminated in this manner, thefilm thickness of an insulating film between the inductors (Ia, Ib) canbe increased. This can improve withstand voltage between the inductorsIa, Ib. In addition, since the polyimide films PI1 and PI2 are formed byrepeating the steps of application, exposure and development, and cure,these films can be formed with good film formability. That is, ifapplication, exposure and development, and cure are performed once toforma thick film, thermal contraction is increased at the thermal dryingstep in development, so that peeling-off of the film is caused or theflatness thereof is deteriorated. On the other hand, if polyimide films(PI1, PI2) are formed in a laminating manner by repeating the steps morethan once, thermal contraction of each film is relatively small, so thatthe adhesiveness of these films is improved, and the flatness thereof isalso improved.

Further, since the polyimide films PI1 and PI2 are so formed in astairs-like shape as to have the steps St1, St2, the occurrence of adepression or peeling-off of the polyimide film PI2 due to defectiveexposure can be reduced. The details will be described later (see FIGS.31 to 33, etc.).

Next, as shown in FIG. 12, on the insulating film IL4 b including thepad region PD1, and the polyimide films PI1 and PI2, a barrier film (notshown) composed of a titanium (Ti) or Chromium (Cr) film, for example,is so deposited as to have a film thickness of about 75 nm by asputtering process or the like, and further, on the barrier film (notshown), a copper thin film (copper film) is so deposited as a Cu seedlayer (power feeding layer) SE for electrolytic plating as to have afilm thickness of about 250 nm by a sputtering process or the like.

Here, according to the first embodiment, since depressions in the endsof the polyimide films PI1, PI2 or peeling-off thereof are reduced, thebarrier film (not shown) or the Cu seed layer SE can be formed with goodcoatability. The details will be described later (see FIGS. 31 to 33,etc.).

Next, as shown in FIG. 13, a photoresist film PR1 is applied on the Cuseed layer SE. Next, as shown in FIG. 14, the photoresist film PR1 isexposed using as a mask a reticle RE1 on which a pattern of inductor Ibhas been drawn. The pattern of inductor Ib can be the shape shown inFIG. 3 described above, for example.

Here, the photoresist film PR1 is qualitatively altered by irradiatingthe photoresist film PR1 with light through a region corresponding tothe pattern of inductor Ib. Next, as shown in FIG. 15, the photoresistfilm PR1 is exposed using as a mask a reticle RE2 on which a pattern ofrewiring RW has been drawn. Here, the photoresist film PR1 isqualitatively altered by irradiating the photoresist film PR1 with lightthrough a region corresponding to the pattern of rewiring RW. Next, asshown in FIG. 16, by a development process, the photoresist film PR1 ina qualitatively-altered region is removed, and thermally dried. Thus,the photoresist film PR1 in inductor Ib and rewiring RW forming regionsis removed, and opening portions (wiring trenches) are formed. Inaddition, the Cu seed layer SE is exposed in the region from which thephotoresist film PR1 has been removed.

Since the polyimide films PIT and PI2 provide a difference in heightbetween the surface of the peripheral circuit forming region 1A and thesurface of the transformer forming region 2A in this manner, thepatterns (the pattern of inductor Ib, the pattern of rewiring RW) can beprecisely transferred to the peripheral circuit forming region 1A andthe transformer forming region 2A by exposing the photoresist film PR1for each region. That is, if a difference in height exists betweentransfer regions (the surface of the peripheral circuit forming region1A and the surface of the transformer forming region 2A) in one-shotexposure (transfer) of patterns (the pattern of inductor Ib, the patternof rewiring RW), it is difficult to set a focal height (position), sothat exposure (transfer) of a desired pattern may fail because ofdefocus in either region. On the other hand, in the first embodiment,exposure can be performed with a reticle (mask) prepared for each regionunder exposure conditions, such as a focal position, optimized for eachregion. Therefore, exposure (transfer) of each pattern (the pattern ofinductor Ib, the pattern of rewiring RW) can be precisely performed.

Next, as shown in FIG. 17, within the opening portions (wiring trenches)of the remaining photoresist film PR1, i.e., on the Cu seed layer SE inthe inductor Ib and rewiring RW forming regions, the inductor Ib and therewiring RW are formed by forming Cu films (copper films) having a filmthickness of about 4 to 10 μm by an electrolytic plating process.

Next, as shown in FIG. 18, a photoresist film PR2 is applied on thephotoresist film PR1 including the inductor Ib and the rewiring RW.Next, as shown in FIG. 19, the photoresist film PR2 is exposed using asa mask a reticle RE3 on which a pattern of a base metal film UM of thetransformer forming region 2A has been. Here, the photoresist film PR2is qualitatively altered by irradiating the photoresist film PR2 withlight through a region corresponding to the pattern of the base metalfilm UM of the transformer forming region 2A. Next, as shown in FIG. 20,the photoresist film PR2 is exposed using as a mask a reticle RE4 onwhich a pattern of the base metal film UM of the peripheral circuitforming region 1A has been drawn. Here, the photoresist film PR2 isqualitatively altered by irradiating the photoresist film PR2 with lightthrough a region corresponding to the pattern of the base metal film UMof the peripheral circuit forming region 1A. Next, as shown in FIG. 21,by a development process, the photoresist film PR2 in aqualitatively-altered region is removed. Thus, the photoresist film PR2in a base metal film UM forming region on the inductor Ib and in a basemetal film UM forming region on the rewiring RW is removed. In addition,the inductor Ib and the rewiring RW are exposed in the respectiveregions from which the photoresist film PR2 has been removed.

Since the polyimide films PI1 and PI2 provide a difference in heightbetween the surface of the peripheral circuit forming region 1A and thesurface of the transformer forming region 2A in this manner, thephotoresist film PR2 is exposed for each of the peripheral circuitforming region 1A and the transformer forming region 2A. Thus, exposure(transfer) of each pattern (the pattern of the base metal film UM on theinductor Ib, the pattern of the base metal film UM on the rewiring RW)can be performed precisely.

Next, as shown in FIG. 22, within the remaining photoresist film PR2,i.e., on the Cu film (the inductor Ib and rewiring RW) in the base metalfilm UM forming regions, a Ni film (nickel film) is so formed as to havea film thickness of about 1.5 μm by an electrolytic plating process.Next, an Au film (gold film) is so formed on the Ni film as to have afilm thickness of about 2 μm by an electrolytic plating process. Thus, abase metal film UM composed of a laminated film (Ni/Au) of the Ni filmand the Au film can be formed.

Next, as shown in FIG. 23, the photoresist films PR1, PR2 are removed.Thus, the Cu seed layer SE is exposed in regions excluding the inductorIb and the rewiring RW.

Next, as shown in FIG. 24, the Cu seed layer SE in regions excluding theinductor Ib and the rewiring RW and the barrier film (not shown)positioned in a layer therebelow are removed by etching. Thus, the Cuseed layer SE and the barrier film (not shown) excluding those locatedin a layer below the inductor Ib and the rewiring RW are removed. Itshould be understood that a laminated film of the Cu seed layer SE, thebarrier film (not shown), and the Cu film can be regarded as theinductor Ib and the rewiring RW.

Next, as shown in FIG. 25, the inductor Ib, a photosensitive polyimidefilm PI3 is applied on the rewiring RW, the polyimide film PI2, and thelike, including the base metal film UM, as an insulating film(protective film). For example, the polyimide film PI3 is formed byrotationally applying a polyimide precursor solution on the surface ofthe SOI substrate 1, and then drying the same. Next, as shown in FIG.26, the polyimide film PI3 is exposed using as a mask a reticle RE5 inwhich pattern portions of the pad region PD2 of the peripheral circuitforming region 1A, the pad region PD2 of the transformer forming region2A, and an opening portion OA have been shielded. Here, the polyimidefilm PI3 is qualitatively altered by irradiating the polyimide film PI3with light through regions excluding forming regions of the pad regionsPD2 and the opening portion OA.

Next, as shown in FIG. 27, opening portions (opening regions, exposedparts of the base metal film UM) are formed by removing the polyimidefilm PI3 from regions excluding qualitatively-altered regions (in otherwords, shielding regions of the reticle RE5) by a development process.Thus, the base metal film UM on the inductor Ib and the base metal filmUM on the rewiring RW are exposed. These exposed regions of the basemetal films UM are the pad regions PD2. In addition, at this time, theopening portion OA is formed in the border between the peripheralcircuit forming region 1A and the transformer forming region 2A. Theinterlayer insulating film IL4 (insulating film IL4 b) is exposed in thebottom of the opening portion OA. Thus, the opening portion (recess) OAexposing at least the interlayer insulating film IL4 (insulating filmIL4 b) is provided by removing the polyimide film PI3 in the borderbetween the peripheral circuit forming region 1A and the transformerforming region 2A. This increases the surface area of the surface of alaminated film of polyimide films (PI1 to PI3) capable of becoming aleak path between the inductors (Ia, Ib), so that leakage current can bereduced. In addition, the reduction in leakage current can improvewithstand voltage. Further, in a case where the polyimide film PI3 of atype that leaves a region which has altered qualitatively by exposure(negative type) is used, exposure amount adjustment is easy without theneed to take into consideration an exposure amount for the borderbetween the peripheral circuit forming region 1A and the transformerforming region 2A.

Incidentally, a “negative type” of the photosensitive film (for example,a photoresist film or a polyimide film) means a type of photosensitivefilm that decreases solubility to a developer when being exposed so thata region which has been altered quantitatively by exposure is left. Onthe other hand, a type of photosensitive film that increases solubilityto a developer when being exposed so that a region which has beenaltered quantitatively by exposure is removed is called “positive type”.For example, the above polyimide films PI1, PI2 and the photoresistfilms PR1, PR2 are of the “positive type”.

Thereafter, the SOI substrate (wafer) 1 is divided (singulated) into aplurality of chips (semiconductor chips) by cutting (dicing). It shouldbe noted that before dicing, the SOI substrate 1 may be thinned bybackside grinding of the SOI substrate 1. Next, the semiconductor chipis mounted (bonded) on a die pad of a lead frame (die bonding). Leads(external terminals, terminals) are provided around the die pad. Next,the pad regions PD2 on the semiconductor chip and the leads areconnected together by wires composed of gold wires (conductive wires,conductive members) (wire bonding, see FIG. 35).

Thereafter, if necessary, the semiconductor chip and the wires areencapsulated (packaged) with encapsulating resin (molding resin) or thelike.

Since the laminated film of the polyimide films PI1 and PI2 is providedbetween the inductors Ia, Ib in the transformer forming region 2A inthis manner in the first embodiment, the film thickness of theinsulating film between the inductors Ia, Ib can be increased. This canimprove withstand voltage between the inductors Ia, Ib. It should benoted that the laminated film of the polyimide films PI1 and PI2 is notprovided in the peripheral circuit forming region 1A. This provides thestep St1 between the interlayer insulating film IL4 (insulating film IL4b) that is an insulating film in a layer below the rewiring RW and thepolyimide film PI1.

In addition, since the polyimide film PI2 is so disposed as to beretreated from the end of the polyimide film PI1 in the laminated filmof the polyimide films PI1 and PI2, the occurrence of a depression orpeeling-off of the polyimide film PI2 due to defective exposure can bereduced.

FIG. 28 is a sectional view of an inductor (Ia, Ib) portion of thesemiconductor device of the first embodiment. As illustrated, the stepSt1 is provided between the interlayer insulating film IL4 (insulatingfilm IL4 b) that is an insulating film in a layer below the rewiring RWand the polyimide film PI1, and the step St2 is provided between thepolyimide films PI1 and PI2.

FIG. 29 is a sectional view showing the configuration of a comparativeexample 1 of the first embodiment. In the comparative example 1, asingle-layer polyimide film PI is provided between the inductors Ia, Ib.The film thickness of the polyimide film PI is about 15 to 25 μm, forexample. Also, FIG. 30 is a sectional view showing the configuration ofa comparative example 2 of the first embodiment. In the comparativeexample 2, the polyimide film PI2 is so disposed as to enclose thepolyimide film PI1. Regarding the single-layer polyimide film PI shownin FIG. 29, since it is difficult to expose the polyimide film PI tolight by single exposure, and defective exposure easily occurs. Inaddition, if the single-layer polyimide film PI is increased in filmthickness, film contraction at the thermally-drying step of thedeveloping process is increased, so that peeling-off of the film at theend of the polyimide film PI easily occurs, and the flatness of the filmsurface can also be deteriorated by the film contraction.

Also, as shown in FIG. 30, defective exposure easily occurs when thepolyimide film PI2 is so disposed as to enclose the polyimide film PI1.According to examinations of the present inventors, a phenomenon hasbeen confirmed that exposure causes the end of the laminated film of thepolyimide films PI1 and PI2 to take an inversely-tapered shape.

FIG. 31 is a sectional view showing schematically that the laminatedfilm of the polyimide films that is the comparative example 2 of thefirst embodiment has been inversely tapered. In addition, FIG. 32 is aphotograph of the inversely tapered laminated film of the polyimidefilms which the present inventors have confirmed. FIG. 33 is a tracingof the shape of the polyimide films in the photograph of FIG. 32. Itshould be noted that in FIGS. 33 and 32 the polyimide film PI1 has atwo-layer structure composed of a polyimide film PI1 a and a polyimidefilm PI1 b.

As shown in FIGS. 31 to 33, if the laminated film of the polyimide filmstakes an inversely-tapered shape, the respective adhesiveness of thepolyimide films are deteriorated, so that the end of the upper-layerpolyimide film peels off. In particular, if the Cu seed layer SE forforming the rewiring RW and the inductor Ib by electrolytic plating isformed thereafter on the laminated film of the polyimide films (see FIG.12), step disconnection of the Cu seed layer SE occurs at a depressionor peeling-off due to defective exposure, so that a plating defectoccurs. For example, insufficient power feeding causes difficulty informing the rewiring RW and the inductor Ib.

On the other hand, in the first embodiment, since the polyimide filmsPI1 and PI2 are laminated, good application properties in forming eachfilm can be obtained, so that each film can be formed with good flatnessor adhesiveness.

Further, in the first embodiment, since the polyimide film PI2 is sodisposed as to be retreated from the end of the polyimide film PI1 inthe laminated film of the polyimide films PI1 and PI2, the occurrence ofa depression or peeling-off of the polyimide film PI2 due to defectiveexposure can be reduced. In addition, since the film formability of theCu seed layer SE can be improved, plating defects can also be reducedwhen the rewiring RW and the inductor Ib are formed by electrolyticplating.

In addition, since the polyimide film PI2 is so disposed as to beretreated from the end of the polyimide film PI1, the polyimide film PI2can be formed on the polyimide film PI1 having good flatness, so thatthe film formability or flatness of the polyimide film PI2 can beimproved.

In addition, since the rewiring RW is utilized to draw out the padregion PD1 up to a desire region (pad region PD2) in the chip, wirebonding can be easily performed.

Second Embodiment

In a second embodiment, an example of an application site of thesemiconductor device described in the first embodiment will bedescribed. FIG. 34 is a block diagram showing the configuration of asemiconductor device of the second embodiment. FIG. 35 is a plan viewshowing the configuration of the semiconductor device of the secondembodiment.

In the semiconductor device shown in FIG. 34, a chip CH1 on a die padDP1 and a chip CH2 on a die pad DP2 are configured to one package.

The chip CH1 has a transformer composed of an inductor I1 connected to atransmission circuit Tx, and an inductor I2. The inductor I2 isconnected to a receiving circuit Rx of the chip CH2 via pad regions PD2and wires W. Incidentally, in FIGS. 34 and 35, pad regions PD2 arerepresented by rectangles.

The chip CH1 also has a receiving circuit Rx and a logic circuit Logic.The logic circuit Logic is connected to the transmission circuit Tx andthe receiving circuit Rx of the chip CH1, and the logic circuit Logic isconnected to a plurality of pad regions PD2.

The chip CH2 has a transformer composed of an inductor I4 connected to atransmission circuit Tx, and an inductor I3. The inductor I3 isconnected to the receiving circuit Rx of the chip CH1 via pad regionsPD2 and wires W.

The chip CH2 also has a receiving circuit Rx and a logic circuit Logic.The logic circuit Logic is connected to the transmission circuit Tx andthe receiving circuit Rx of the chip CH2, and the logic circuit Logic isconnected to a plurality of pad regions PD2.

As shown in FIG. 35, the inductor I2 of the chip CH1 is connected to thereceiving circuit Rx of the chip CH2 via the wires W. An inductor (I1)(not shown) is disposed in a layer below the inductor I2, and connectedto the transmission circuit Tx of the chip CH1 via a wiring (not shown).

Further, the inductor I3 of the chip CH2 is connected to the receivingcircuit Rx of the chip CH1 via a wire W. An inductor (I4) (not shown) isdisposed in a layer below the inductor I3, and connected to thetransmission circuit Tx of the chip CH2 via a wiring (not shown).

For example, the logic circuit Logic is disposed on the chip CH2. In thechip CH2, peripheral circuits including the logic circuit Logic, thetransmission circuit Tx, the receiving circuit Rx, and the like, areconnected to a plurality of pad regions PD2 via wirings (not shown).Also, in the chip CH1, peripheral circuits including the logic circuitLogic, the transmission circuit Tx, the receiving circuit Rx, and thelike, are connected to a plurality of pad regions PD2 via wirings (notshown).

The pad regions PD2 of the chips CH1 and CH2 are connected to leads RDvia wires W.

In such a semiconductor device, the configuration of the firstembodiment (see FIG. 2, etc.) can be applied to a peripheral circuitpart composed of the logic circuit Logic, the transmission circuit Tx,the receiving circuit Rx, and the like, and a transformer (inductors I1,I2) part of the chip CH2.

Also, the configuration of the first embodiment (see FIG. 2, etc.) canbe applied to a peripheral circuit part composed of the logic circuitLogic, the transmission circuit Tx, the receiving circuit Rx, and thelike, and a transformer (inductors I3, I4) part of the chip CH1.

Third Embodiment Description of Structure

FIGS. 36 to 38 are a plan view or a sectional view showing schematicallythe configuration of a semiconductor device of a third embodiment. FIG.36 corresponds to the plan view, FIG. 37 a sectional view taken along aline A1-A2 in FIG. 36, and FIG. 38 a sectional view taken along a lineB1-B2 in FIG. 36.

In the semiconductor device shown in FIG. 36, a chip CH1 and a chip CH2are integrated in one package.

The chip CH1 has a transformer composed of an upper-layer inductor Iaand a lower-layer inductor (not shown). A transformer forming region isa substantially-rectangular region, a step St3 is disposed therearound,and further a step St2 is disposed around the step St3. In addition, astep St1 is disposed around the step St2.

The chip CH2 also has a transformer composed of an upper-layer inductorIa and a lower-layer inductor (not shown). A transformer forming regionis a substantially-rectangular region, a step St3 is disposedtherearound, and further a step St2 is disposed around the step St3. Inaddition, a step St1 is disposed around the step St2. Each of the stepsSt1 to St3 will be described in detail later with reference to thesectional views (FIGS. 37, 38).

Pad regions PD2 are disposed around each of the chips CH1, CH2.

In addition, in the chip CH2, rewirings RW are so disposed as to connectthe tops of the pad regions PD1. Further, the pad regions PD2 aredisposed on the rewirings RW.

The pad regions PD2 of the chips CH1 and CH2 are connected to leads viawires (see FIG. 35).

Further details will be described with reference to FIGS. 37 and 38.

Each chip CH1, CH2 of the semiconductor device of the third embodimentis formed utilizing an SOI substrate. For example, as shown in FIGS. 37and 38, the chip CH2 is formed on an SOI substrate 1 having a peripheralcircuit forming region 1A and a transformer forming region 2A.

The SOI substrate 1 has a supporting substrate 1 a, an insulating layer1 b formed on the supporting substrate 1 a, and a semiconductor layerformed on the insulating layer 1 b.

N-channel type MISFETs (NT) and p-channel type MISFETs (PT) are formedin the peripheral circuit forming region 1A. An interlayer insulatingfilm IL1 is formed on these MISFETs, and first-layer wirings M1 areformed on the interlayer insulating film IL1. The MISFETs (NT, PT) andthe first-layer wirings M1 are connected together via plugs P1. Inaddition, second-layer wirings M2 are formed on the first-layer wiringsM1 via an interlayer insulating film IL2. The first-layer wirings M1 andthe second-layer wirings M2 are connected together via plugs (not shown)formed in the interlayer insulating film IL2. Third-layer wirings M3 areformed on the second-layer wirings M2 via interlayer insulating filmIL3. The second-layer wirings M2 and the third-layer wirings M3 areconnected together via plugs P3 formed in the interlayer insulating filmIL3.

Rewirings RW are formed on the third-layer wirings M3 via an interlayerinsulating film (an insulating film, a protective film) IL4. Theinterlayer insulating film IL4 is composed of a laminated film of aninsulating film IL4 a and an insulating film IL4 b on the insulatingfilm IL4 a. The rewirings RW are wirings (also referred to asfourth-layer wirings M4) that draw out the pad regions PD1, which areparts of an uppermost-layer wiring (here, the third-layer wirings M3),to desired regions (pad regions PD2) of the chip.

A transformer having an inductor Ia and an inductor Ib is formed in thetransformer forming region 2A. The lower-layer inductor Ia is formed inthe same layer as the third-layer wirings M3. The lower-layer inductorIa is connected to the second-layer wirings M2 in a layer therebelow viaa plurality of plugs P3. That is, the inductor Ia and the second-layerwirings M2 connected to the inductor Ia have the following relationship.The second-layer wirings M2 are wirings that are formed between theinterlayer insulating film IL3 and the interlayer insulating film IL2,and that overlap with the inductor Ia in a plan view. In addition, asviewed in a cross section, the inductor Ia is covered with theinterlayer insulating film IL4, and the inductor Ia and the second-layerwirings M2 are connected together via a plurality of plugs (connectingportions) P3 penetrating the interlayer insulating film IL3.

The inductor Ib is formed on the inductor Ia via the interlayerinsulating film IL4 and polyimide films PI1 and PI2. The polyimide filmsPI1 and PI2 are not formed in the peripheral circuit forming region 1A.That is, the step St1 is formed between the interlayer insulating filmIL4 (insulating film IL4 b) and the polyimide film PI1. The polyimidefilm PI1 is formed on a main surface of the interlayer insulating filmIL4. The polyimide film PI1 has a main surface and side surfacescontinuous with this main surface. In addition, the polyimide film PI2is formed on the main surface of the polyimide film PI1. The polyimidefilm PI2 has a main surface and side surfaces continuous with this mainsurface. Therefore, the step St1 is formed by the main surface of theinterlayer insulating film IL4 and the side surfaces of the polyimidefilm PI1.

Thus, a difference in height corresponding to the film thickness of thepolyimide films PI1 and PI2 (laminated film, laminated insulating film)exists between the forming position of the inductor Ia and the formingpositions of the rewirings RW, but the inductor Ia and the rewirings RWare formed of the same material (the same step). Further, the polyimidefilm PI2 is so formed as to be retreated from an end of the polyimidefilm PI1. In other words, the polyimide films PI1 and PI2 are formed ina stairs-like shape (pyramid shape). That is, the step St2 is formedbetween the polyimide films PI1 and PI2. In other words, the polyimidefilms PI1 and PI2 are a laminated insulating film having the step St2formed by the main surface of the polyimide film PI1 and the mainsurface of the polyimide film PI2 via the side surfaces of the polyimidefilm PI2.

Since the laminated structure of the polyimide films PI1 and PI2 isadopted in this manner, the film thickness of the insulating filmbetween the inductors Ia, Ib can be increased, as described in detail inthe first embodiment. This can improve withstand voltage between theinductors Ia, Ib.

Further, since the polyimide films PI1 and PI2 are so formed in astairs-like shape as to have the steps St1, St2, the film formability ofthe polyimide films PI1 and PI2 can be improved, so that peeling-off ofthe polyimide films PI1 and PI2 can be reduced, as described in detailin the first embodiment.

A polyimide film PI3 is formed on the rewirings RW and the inductor Ia.The polyimide film 3 is formed on the main surface of the polyimide filmPI2. The polyimide film PI3 has a main surface and side surfacescontinuous with this main surface. In addition, the polyimide film PI3is so formed as to be retreated from an end of the polyimide film PI2.In other words, in the transformer forming region 2A, the step St3 isformed between the polyimide film PI2 and the polyimide film PI3. Thatis, the main surface of the polyimide film PI2 and the main surface ofthe polyimide film PI3 form the step St3 via the side surfaces of thepolyimide film PI3. In addition, the polyimide film PI3 has a mainsurface and side surfaces continuous with the main surface. In addition,an opening portion (recess) OA exposing at least the interlayerinsulating film IL4 (insulating film IL4 b) is formed by removing thepolyimide film PI3 in the border between the peripheral circuit formingregion 1A and the transformer forming region 2A.

Regarding the configuration the inductors, it is preferred that aconductive film having a spiral planar shape be used, as describedabove. Here, two spiral conductive films are so disposed as to besymmetrical with respect to the center line of a pad region PD2 locatedin the center of FIG. 3 (see FIG. 36, FIG. 3).

[Manufacturing Method Description]

Next, with reference to FIGS. 37 and 38, a method of manufacturing thesemiconductor device of the third embodiment will be described, and theconfiguration of the semiconductor device thereof will be made clearer.It should be noted that detailed descriptions of the same steps as stepsdescribed in the first embodiment will be omitted.

As shown in FIGS. 37 and 38, for example, an SOI substrate 1 is preparedas the semiconductor substrate. The SOI substrate 1 is composed of asupporting substrate 1 a composed of silicon single crystal(semiconductor film), an insulating layer 1 b formed on the supportingsubstrate 1 a, and a silicon layer 1 c formed on the insulating layer 1b. The SOI substrate 1 has a peripheral circuit forming region 1A and atransformer forming region 2A.

Next, a device isolation insulating film. STI is formed in the siliconlayer 1 c of the SOI substrate 1. This device isolation region can beformed in the same manner as in the first embodiment by means of an STIprocess, for example.

For example, device isolation trenches are formed in the silicon layer 1c of the SOI substrate 1 by means of a photolithography technique and anetching technique. Next, on the SOI substrate 1, a silicon oxide film isso deposited, by means of a CVD process or the like, so as to have afilm thickness just enough to fill the device isolation trenches, andthe silicon oxide film other than the device isolation trenches isremoved by means of a chemical mechanical polishing process, anetching-back process, or the like. Thus, the silicon oxide film can beburied in the device isolation trenches.

Next, MISFETs (NT, PT) are formed in the peripheral circuit formingregion 1A. Although the method of forming the MISFETs is not limited, aMISFET (NT, PT) having a source-drain region (SD) having an LDDstructure having a high-concentration impurity region and alow-concentration impurity region can be formed in the same manner as inthe first embodiment, for example.

Next, an interlayer insulating film IL1 is formed on the SOI substrate 1including on the MISFETs (NT, PT). For example, after a silicon oxidefilm is deposited by a CVD process, the surface of the interlayerinsulating film IL1 is planarized by a CMP process or the like, ifnecessary.

Next, contact holes are formed by patterning the interlayer insulatingfilm IL1. Next, plugs P1 are formed by burying a conductive film in thecontact holes.

Next, on the interlayer insulating film IL1 and the plugs P1, alaminated film is formed as a conductive film by sequentially depositinga titanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, first-layer wirings M1 are formed on theplugs P1 by patterning the laminated film by means of thephotolithography technique and the etching technique.

Next, an interlayer insulating film IL2 composed of a silicon oxide filmis formed on the first-layer wirings M1 by a CVD process or the like.Next, contact holes are formed in the first-layer wirings M1 bypatterning the interlayer insulating film IL2.

Next, plugs (not shown) are formed in the interlayer insulating film IL2by burying a conductive film in the contact holes. These plugs can beformed in the same manner as the plugs P1.

Next, on the interlayer insulating film IL2 and the plugs, a laminatedfilm is formed as a conductive film by sequentially depositing atitanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, second-layer wirings M2 are formed on theplugs by patterning the laminated film by means of the photolithographytechnique and the etching technique.

Next, an interlayer insulating film IL3 composed of a silicon oxide filmis formed on the second-layer wirings M2 by a CVD process or the like.Next, contact holes are formed in the second-layer wirings M2 bypatterning the interlayer insulating film IL3.

Next, plugs P3 are formed in the interlayer insulating film IL3 byburying a conductive film in the contact holes. These plugs can beformed in the same manner as the plugs P1.

Next, on the interlayer insulating film IL3 and the plugs, a laminatedfilm is formed as a conductive film by sequentially depositing atitanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, third-layer wirings M3 are formed on theplugs by patterning the laminated film by means of the photolithographytechnique and the etching technique.

Here, in the transformer forming region 2A, a lower-layer inductor Ia isformed in the same layer as the third-layer wirings M3. That is, at thetime of patterning the laminated film, the above-described spiralconductive films (inductor Ia) are formed in the transformer formingregion 2A (see FIG. 37, FIG. 38). It should be noted that the conductivefilms (inductor Ia) are connected to the second-layer wirings M2 in alayer therebelow via the plugs P3 (see FIG. 38).

Next, an insulating film IL4 a is formed on the third-layer wirings M3(here, the uppermost-layer wirings) and the interlayer insulating filmIL3. For example, the insulating film IL4 a is formed by depositing asilicon nitride film by a CVD process or the like.

Next, a photosensitive polyimide film, for example, is applied on theinsulating film IL4 a as an insulating film IL4 b. For example, thepolyimide film is formed by rotationally applying a polyimide precursorsolution on the surface of the SOI substrate 1, and then drying thesame. Next, opening portions (opening regions, exposed portions of thethird-layer wirings M3) are formed by removing the polyimide film (IL4b) in the pad regions PD1 by exposing and developing the photosensitivepolyimide film (IL4 b). Thereafter, the polyimide film (IL4 b) is curedby a thermal treatment. The film thickness of the polyimide film (IL4 b)is about 3 to 10 μm, for example. Next, the third-layer wirings M3 inthe pad regions PD1 are exposed by removing the insulating film IL4 a byetching. Thus, the interlayer insulating film IL4 having the openingportions in the pad regions PD1 and composed of a laminated film of theinsulating film IL4 a and the insulating film IL4 b is formed.

Next, a photosensitive polyimide film PI1 is applied on the insulatingfilm IL4 b including the pad regions PD1 as a first insulating film (aninterlayer insulating film, an insulating film for ensuring withstandvoltage, an insulating film between the inductors). The film thicknessof the polyimide film PI1 is about 3 to 10 μm, for example. Here, sincethe insulating film IL4 b extends from the transformer forming region 2Ato the peripheral circuit forming region 1A, a step St1 is formedbetween the insulating film IL4 b and the polyimide film PI1.

Next, a photosensitive polyimide film PI2 is applied on the insulatingfilm IL4 b including the pad regions PD1 and the polyimide film PI1 as asecond insulating film. For example, the polyimide film PI2 is formed byrotationally applying a polyimide precursor solution on the surface ofthe SOI substrate 1, and then drying the same. Next, the polyimide filmPI2 in the peripheral circuit forming region 1A is removed by exposingand developing the photosensitive polyimide film PI2. At this time, thepolyimide film PI2 is retreated from the end of the polyimide film PI1.Thus, the end of the polyimide film PI1 is exposed, and a step St2 isformed between the polyimide film PI1 and the polyimide film PI2.Thereafter, the polyimide film PI2 is cured by a thermal treatment. Thefilm thickness of the polyimide film PI1 is about 3 to 10 μm, forexample. Further, the retreat amount of the polyimide film PI2, i.e., adistance between the end of the polyimide film PI1 and the end of thepolyimide film PI2 (step width) is 50 μm to 100 μm, for example.

Since the polyimide films PI1 and PI2 are laminated in this manner, thefilm thickness of an insulating film between the inductors (Ia, Ib) canbe increased.

Further, since the polyimide films PI1 and PI2 are so formed in astairs-like shape as to have the steps St1, St2, the occurrence of adepression or peeling-off of the polyimide film PI2 due to defectiveexposure can be reduced, as described in detail in the first embodiment.

Next, on the insulating film IL4 b including the pad region PD1 and thepolyimide films PI1 and PI2, a barrier film (not shown) composed of atitanium (Ti) or Chromium (Cr) film, for example, is deposited by asputtering process or the like, and further, on the barrier film (notshown), a copper thin film (copper film) is deposited as a Cu seed layer(not shown) for electrolytic plating by a sputtering process or thelike.

Here, according to the third embodiment, since depressions in the endsof the polyimide films PI1, PI2 or peeling-off thereof are reduced, thebarrier film (not shown) or the Cu seed layer SE can be formed with goodcoatability.

Next, in the same manner as in the first embodiment, an inductor Ib andrewirings RW are formed on the Cu seed layer (not shown). Further, abase metal film UM composed of a laminated film of a Ni film and an Aufilm (Ni/Au) is formed on the inductor Ib and the rewirings RW.

Next, a photosensitive polyimide film PI3 is applied, as an insulatingfilm (protective film), on top of the inductor Ib including the basemetal film UM, the rewirings RW, the polyimide film PI2, and the like.For example, the polyimide film PI3 is formed by rotationally applying apolyimide precursor solution on the surface of the SOI substrate 1, andthen drying the same. Next, the polyimide film PI3 is exposed using, asa mask, a reticle in which pattern portions of the pad regions PD2 ofthe peripheral circuit forming region 1A, the pad regions PD2 of thetransformer forming region 2A, and an opening portion OA have beenshielded.

Next, opening portions (opening regions, exposed portions of the basemetal film UM) are formed by removing the polyimide film PI3 other thanqualitatively-altered regions (i.e., shielded regions of the reticle) bya development process. Thus, the base metal film UM on the inductor Iband the base metal film UM on the rewirings RW are exposed. The exposedregions of the base metal film UM become the pad regions PD2. Inaddition, at this time, the opening portion OA is formed in the borderbetween the peripheral circuit forming region 1A and the transformerforming region 2A. The interlayer insulating film IL4 (insulating filmIL4 b) is exposed from the bottom of the opening portion OA. In thismanner, the opening portion (recess) OA exposing at least the interlayerinsulating film IL4 (insulating film IL4 b) is provided by removing thepolyimide film PI3 in the border between the peripheral circuit formingregion 1A and the transformer forming region 2A.

Thereafter, the SOI substrate (wafer) 1 is divided (singulated) into aplurality of chips (semiconductor chips) by cutting (dicing) the SOIsubstrate 1. It should be noted that before dicing, the SOI substrate 1may be thinned by backside grinding of the SOI substrate 1. Next, thesemiconductor chip is mounted (bonded) on a die pad of a lead frame (diebonding). Leads (external terminals, terminals) are provided around thedie pad. Next, the pad regions PD2 on the semiconductor chip and theleads are connected together by wires composed of gold wires (conductivewires, conductive members) (wire bonding, see FIG. 35).

Thereafter, if necessary, the semiconductor chip and the wires areencapsulated (packaged) with encapsulating resin (molding resin) or thelike.

Since the laminated film of the polyimide films PI1 and PI2 is providedbetween the inductors Ia, Ib in the transformer forming region 2A inthis manner in the third embodiment, the film thickness of theinsulating film between the inductors Ia, Ib can be increased. This canimprove withstand voltage between the inductors Ia, Ib.

In addition, since the polyimide film PI2 is so disposed as to beretreated from the end of the polyimide film PI1 in the laminated filmof the polyimide films PI1 and PI2, the occurrence of depressions orpeeling-off of the polyimide film PI2 due to defective exposure can bereduced.

In addition, since the rewirings RW are covered with the polyimide filmPI3, the rewirings RW can be protected. In addition, since the inductorIb is covered with the polyimide film PI3, the inductor Ib can beprotected. In addition, since the polyimide film PI3 is so formed as tobe retreated from the end of the polyimide film PI2, and the laminatedfilm of the polyimide films (PI1 to PI3) is formed in a stairs-likeshape (pyramid shape) in the transformer forming region 2A, thefollowing advantageous effects are obtained.

In FIG. 38, a creepage distance (a shortest distance between twoconductive portions along the surface of an insulating film) isrepresented by a dashed two-dotted line. In order to achieve electricalinsulation without isolation by an insulator, it is necessary to secureboth a spatial distance and a creepage distance. Here, in the thirdembodiment, since the steps (St1 to St3) are formed when the insulatingfilms (PI1 to PI3) are laminated, a trench composed of multi-stage sidewalls of the insulating film insulator is formed between electrodes of ahigh withstand voltage and a low withstand voltage, namely, between thepad regions PD2 of the peripheral circuit forming region 1A and the padregions PD2 of the transformer forming region 2A by combining theplurality of steps with each other, so that a high withstand-voltageregion and a low withstand-voltage region are separated from each other.This can gain a longer creepage distance, so that a highwithstand-voltage electrically-insulated state can be achieved.

Further, in the third embodiment, as shown in the peripheral circuitforming region 1A in FIG. 38, the plurality of pad regions PD1 are drawnout to the pad regions PD2 by means of the rewirings RW. Specifically,source electrodes (or drain electrodes) of a plurality of MISFETs (NT,PT) are connected by the rewirings RW and drawn out to the pad regionsPD2. This makes it possible to lower resistance as compared with thecase where the pad regions PD1 are connected by the lower-layer wirings(M1 to M3) composed of Al or the like. That is, Cu that constitutes therewirings RW has lower resistance than Al, and regarding the rewiringsRW located in the upper layer, wiring resistance can be lowered becausethe wiring can be thickly formed. In addition, since the pad regions PD2are disposed in the vicinity of the center of the rewirings(strip-shaped straight line), as shown in FIG. 36, current can beequally distributed (or collected) from the individual source electrodes(or drain electrodes) of the MISFETs (NT, PT), so that the loads appliedto the individual MISFETs can be more equalized.

Fourth Embodiment

The laminated film of the polyimide films PI1 and PI2 has been providedbetween the inductors Ia, Ib in the transformer forming region 2A in thefirst to third embodiments, but the film thickness of the insulatingfilm between the inductors Ia, Ib can be reduced when required withstandvoltage is small. In this case, the insulating film between theinductors Ia, Ib may be a single layer.

[Description of Description]

FIGS. 39 to 41 are a plan view or a sectional view schematically showingthe configuration of the semiconductor device of a fourth embodiment.FIG. 39 corresponds to a plan view, FIG. 40 a sectional view taken alonga line C1-C2 in FIG. 39, and FIG. 41 a sectional view taken along a lineD1-D2 in FIG. 39.

In the semiconductor device shown in FIG. 39 a chip CH1 and a chip CH2are integrated in one package.

The chip CH1 has a transformer composed of an upper-layer inductor Iaand a lower-layer inductor (not shown). A forming region of thetransformer is a substantially-rectangular region, a step St3 isdisposed therearound, and further a step St1 is disposed around the stepSt3.

The chip CH2 also has a transformer composed of an upper-layer inductorIa and a lower-layer inductor (not shown). A forming region of thetransformer is a substantially-rectangular region, a step St3 isdisposed therearound, and further a step St1 is disposed around the stepSt3. Each of the steps St1, St3 will be described in detail later withreference to the sectional views (FIGS. 40, 41).

Pad regions PD2 are disposed around each of the chips CH1, CH2.

Further, in the chip CH2, rewirings RW are so disposed as to connect thetops of the pad regions PD1. Further, the pad regions PD2 are disposedon the rewirings RW.

The pad regions PD2 of the chips CH1 and CH2 are connected to leads viawires (see FIG. 35).

Further details will be described with reference to FIGS. 40 and 41.

Each chip CH1, CH2 of the semiconductor device of the fourth embodimentis formed utilizing an SOI substrate. For example, as shown in FIGS. 40and 41, the chip CH2 is formed on an SOI substrate 1 having a peripheralcircuit forming region 1A and a transformer forming region 2A.

The SOI substrate 1 has a supporting substrate 1 a, an insulating layer1 b formed on the supporting substrate 1 a, and a semiconductor layerformed on the insulating layer 1 b.

N-channel type MISFETs (NT) and p-channel type MISFETs (PT) are formedin the peripheral circuit forming region 1A. An interlayer insulatingfilm IL1 is formed on these MISFETs, and first-layer wirings M1 areformed on the interlayer insulating film IL1. The MISFETs (NT, PT) andthe first-layer wirings M1 are connected together via plugs P1. Inaddition, second-layer wirings M2 are formed on the first-layer wiringsM1 via an interlayer insulating film IL2. The first-layer wirings M1 andthe second-layer M2 are connected together via plugs (not shown) formedin the interlayer insulating film IL2. Third-layer wirings M3 are formedon the second-layer wirings M2 via interlayer insulating film IL3. Thesecond-layer wirings M2 and the third-layer wirings M3 are connectedtogether via plugs P3 formed in the interlayer insulating film IL3.

Rewirings RW are formed on the third-layer wirings M3 via an interlayerinsulating film (an insulating film, a protective film) IL4. Theinterlayer insulating film IL4 is composed of a laminated film of aninsulating film IL4 a and an insulating film IL4 b on the insulatingfilm IL4 a. The rewirings RW are wirings (also referred to asfourth-layer wirings M4) that draw out the pad regions PD1, which areparts of an uppermost-layer wiring (here, the third-layer wirings M3),to desired regions (pad regions PD2) of the chip.

A transformer having an inductor Ia and an inductor Ib is formed in thetransformer forming region 2A. The lower-layer inductor Ia is formed inthe same layer as the third-layer wirings M3. The lower-layer inductorIa is connected to the second-layer wirings M2 in a layer therebelow viaa plurality of plugs P3. That is, the inductor Ia and the second-layerwirings M2 connected to the inductor Ia have the following relationship.The second-layer wirings M2 are wirings that are formed between theinterlayer insulating film IL3 and the interlayer insulating film IL2,and that overlap with the inductor Ia in a plan view. In addition, asviewed in a cross section, the inductor Ia is covered with theinterlayer insulating film IL4, and the inductor Ia and the second-layerwirings M2 are connected together via a plurality of plugs (connectingportions) P3 penetrating the interlayer insulating film IL3.

The inductor Ib is formed on the inductor Ia via the interlayerinsulating film IL4 and a polyimide film PI1. The polyimide film PI1 isnot formed in the peripheral circuit forming region 1A. That is, thestep St1 is formed between the interlayer insulating film IL4(insulating film IL4 b) and the polyimide film PI1. The polyimide filmPI1 is formed on a main surface of the interlayer insulating film IL4.The polyimide film PI1 has a main surface and side surfaces continuouswith this main surface. Therefore, the step St1 is formed by the mainsurface of the interlayer insulating film IL4 and the side surfaces ofthe polyimide film PI1.

Thus, a difference in height corresponding to the film thickness of thepolyimide film PI1 exists between the forming position of the inductorIa and the forming positions of the rewirings RW, but the inductor Iaand the rewirings RW are formed of the same material (the same step).

A polyimide film PI3 is formed on the rewirings RW and the inductor Ia.The polyimide film PI3 is formed on the main surface of the polyimidefilm PI1. The polyimide film PI3 has a main surface and side surfacescontinuous with this main surface. In addition, the polyimide film PI3is so formed as to be retreated from an end of the polyimide film PI1.In other words, in the transformer forming region 2A, the step St3 isformed between the polyimide film PI1 and the polyimide film PI3. Thatis, the main surface of the polyimide film PI1 and the main surface ofthe polyimide film PI3 form the step St3 via the side surfaces of thepolyimide film PI3. In addition, the polyimide film PI3 has a mainsurface and side surfaces continuous with the main surface. In addition,an opening portion (recess) OA exposing at least the interlayerinsulating film IL4 (insulating film IL4 b) is formed by removing thepolyimide film PI3 in the border between the peripheral circuit formingregion 1A and the transformer forming region 2A.

Regarding the configuration the inductors, it is preferred that aconductive film having a spiral planar shape be used, as describedabove. Here, two spiral conductive films are so disposed as to besymmetrical with respect to the center line of a pad region PD2 locatedin the center of FIG. 39 (see FIG. 39, FIG. 3).

[Manufacturing Method Description]

Next, with reference to FIGS. 40 and 41, a method of manufacturing thesemiconductor device of the fourth embodiment will be described, and theconfiguration of the semiconductor device thereof will be made clearer.It should be noted that detailed descriptions of the same steps as stepsdescribed in the first embodiment will be omitted.

As shown in FIGS. 40 and 41, for example, an SOI substrate 1 is preparedas the semiconductor substrate. The SOI substrate 1 is composed of asupporting substrate 1 a composed of silicon single crystal(semiconductor film), an insulating layer 1 b formed on the supportingsubstrate 1 a, and a silicon layer 1 c formed on the insulating layer 1b. The SOI substrate 1 has a peripheral circuit forming region 1A and atransformer forming region 2A.

Next, a device isolation insulating film STI is formed in the siliconlayer 1 c of the SOI substrate 1. This device isolation film can beformed in the same manner as in the first embodiment by means of an STIprocess, for example.

For example, device isolation trenches are formed in the silicon layer 1c of the SOI substrate 1 by means of a photolithography technique and anetching technique. Next, on the SOI substrate 1, a silicon oxide film isdeposited, by means of a CVD process or the like, so as to have athickness just enough to fill the device isolation trenches, and thesilicon oxide film other than the device isolation trenches is removedby means of a chemical mechanical polishing process, an etching-backprocess, or the like. Thus, the device isolation trenches can be filledwith the silicon oxide film.

Next, MISFETs (NT, PT) are formed in the peripheral circuit formingregion 1A. Although the method of forming the MISFETs is not limited, aMISFET (NT, PT) having a source-drain region (SD) having an LDDstructure having a high-concentration impurity region and alow-concentration impurity region can be formed in the same manner as inthe first embodiment, for example.

Next, an interlayer insulating film IL1 is formed on the SOI substrate 1including on the MISFETs (NT, PT). For example, after a silicon oxidefilm is deposited by a CVD process, the surface of the interlayerinsulating film IL1 is planarized by a CMP process or the like, ifnecessary.

Next, contact holes are formed by patterning the interlayer insulatingfilm IL1. Next, plugs P1 are formed by burying a conductive film in thecontact holes.

Next, on the interlayer insulating film IL1 and the plugs P1, alaminated film is formed as a conductive film by sequentially depositinga titanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, first-layer wirings M1 are formed on theplugs P1 by patterning the laminated film by means of thephotolithography technique and the etching technique.

Next, an interlayer insulating film IL2 composed of a silicon oxide filmis formed on the first-layer wirings M1 by a CVD process or the like.Next, contact holes (not shown) are formed on the first-layer wirings M1by patterning the interlayer insulating film IL2.

Next, plugs (not shown) are formed in the interlayer insulating film IL2by burying a conductive film in the contact holes. These plugs can beformed in the same manner as the plugs P1.

Next, on the interlayer insulating film IL2 and the plugs, a laminatedfilm is formed as a conductive film by sequentially depositing atitanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, second-layer wirings M2 are formed on theplugs by patterning the laminated film by means of the photolithographytechnique and the etching technique.

Next, an interlayer insulating film IL3 composed of a silicon oxide filmis formed on the second-layer wirings M2 by a CVD process or the like.Next, contact holes are formed on the second-layer wirings M2 bypatterning the interlayer insulating film IL3.

Next, plugs P3 are formed in the interlayer insulating film IL3 byburying a conductive film in the contact holes. These plugs can beformed in the same manner as the plugs P1.

Next, on the interlayer insulating film IL3 and the plugs, a laminatedfilm is formed as a conductive film by sequentially depositing atitanium/titanium-nitride film, an aluminum film, and atitanium/titanium-nitride film, for example, by means of a sputteringprocess or the like. Next, third-layer wirings M3 are formed on theplugs by patterning the laminated film by means of the photolithographytechnique and the etching technique.

Here, in the transformer forming region 2A, a lower-layer inductor Ia isformed in the same layer as the third-layer wirings M3. That is, at thetime of patterning the laminated film, the above-described spiralconductive films (inductor Ia) are formed in the transformer formingregion 2A (see FIG. 40, FIG. 41). It should be noted that the conductivefilms (inductor Ia) are connected to the second-layer wirings M2 in alayer therebelow via the plugs P3 (see FIG. 41).

Next, an insulating film IL4 a is formed on the third-layer wirings M3(here, the uppermost-layer wirings) and the interlayer insulating filmIL3. For example, the insulating film IL4 a is formed by depositing asilicon nitride film so as to have a film thickness of about 1 to 4 μmby a CVD process or the like.

Next, for example, a photosensitive polyimide film is applied on theinsulating film IL4 a as an insulating film IL4 b. For example, thepolyimide film is formed by rotationally applying a polyimide precursorsolution on the surface of the SOI substrate 1, and then drying thesame. Next, opening portions (opening regions, exposed portions of thethird-layer wirings M3) are formed by removing the polyimide film (IL4b) in the pad regions PD1 by exposing and developing the photosensitivepolyimide film (IL4 b). Thereafter, the polyimide film (IL4 b) is curedby a thermal treatment. The film thickness of the polyimide film (IL4 b)is about 3 to 10 μm, for example. Next, the third-layer wirings M3 inthe pad regions PD1 are exposed by removing the insulating film IL4 a byetching. Thus, the interlayer insulating film IL4 having the openingportions in the pad regions PD1 and composed of a laminated film of theinsulating film IL4 a and the insulating film IL4 b is formed.

Next, a photosensitive polyimide film PI1 is applied to the insulatingfilm IL4 b including the pad regions PD1 as a first insulating film (aninterlayer insulating film, an insulating film for ensuring withstandvoltage, an insulating film between inductors). The film thickness ofthe polyimide film PI1 is about 11 μm, for example. Here, since theinsulating film IL4 b extends from the transformer forming region 2A tothe peripheral circuit forming region 1A, a step St1 is formed betweenthe insulating film IL4 b and the polyimide film PI1.

Next, in the same manner as in the first embodiment, an inductor Ib andrewirings RW are formed. Further, a base metal film UM composed of alaminated film of a Ni film and an Au film (Ni/Au) is formed on theinductor Ib and the rewirings RW.

Next, a photosensitive polyimide film PI3 is applied, as an insulatingfilm (protective film), on top of the inductor Ib including the basemetal film UM, the rewirings RW, the polyimide film PI1, and the like.For example, the polyimide film PI3 is formed by rotationally applying apolyimide precursor solution on the surface of the SOI substrate 1, andthen drying the same. Next, the polyimide film PI3 is exposed using, asa mask, a reticle in which pattern portions of the pad regions PD2 ofthe peripheral circuit forming region 1A, the pad regions PD2 of thetransformer forming region 2A, and an opening portion OA have beenshielded.

Next, opening portions (opening regions, exposed portions of the basemetal film UM) are formed by removing the polyimide film PI3 other thanqualitatively-altered regions (i.e., shielded regions of the reticle) bya development process. Thus, the base metal film UM on the inductor Iband the base metal film UM on the rewirings RW are exposed. The exposedregions of the base metal film UM become the pad regions PD2. Inaddition, at this time, the opening portion OA is formed in the borderbetween the peripheral circuit forming region 1A and the transformerforming region 2A. The interlayer insulating film IL4 (insulating filmIL4 b) is exposed from the bottom of the opening portion OA. In thismanner, the opening portion (recess) OA exposing at least the interlayerinsulating film IL4 (insulating film IL4 b) is provided by removing thepolyimide film PI3 in the border between the peripheral circuit formingregion 1A and the transformer forming region 2A.

Thereafter, the SOI substrate (wafer) 1 is divided (singulated) into aplurality of chips (semiconductor chips) by cutting (dicing) the SOIsubstrate 1. It should be noted that before dicing, the SOI substrate 1may be thinned by backside grinding of the SOI substrate 1. Next, thesemiconductor chip is mounted (bonded) on a die pad of a lead frame (diebonding). Leads (external terminals, terminals) are provided around thedie pad. Next, the pad regions PD2 on the semiconductor chip and theleads are connected together by wires composed of gold wires (conductivewires, conductive members) (wire bonding, see FIG. 35).

Thereafter, if necessary, the semiconductor chip and the wires areencapsulated (packaged) with encapsulating resin (molding resin) or thelike.

In this manner, in the fourth embodiment, the single layer of thepolyimide film PI1 is provided between the inductors Ia, Ib in thetransformer forming region 2A.

Further, in the fourth embodiment, since the rewirings RW are coveredwith the polyimide film PI3, the rewirings RW can be protected. Inaddition, since the inductor Ib is covered with the polyimide film PI3,the inductor Ib can be protected. Moreover, since the polyimide film PI3is so formed as to be retreated from the end of the polyimide film PI1,and the laminated film of the polyimide films (PI1 to PI3) is formed ina stairs-like shape (pyramid shape) in the transformer forming region2A, the following advantageous effects are obtained.

In FIG. 41, a creepage distance (a shortest distance between twoconductive portions along the surface of an insulating film) isrepresented by a dashed two-dotted line. In order to achieve electricalinsulation without isolation by an insulator, it is necessary to secureboth a spatial distance and a creepage distance. Here, in the fourthembodiment, since the steps (St1, St3) are formed when the insulatingfilms (PI1, PI3) are laminated, a trench composed of multi-stage sidewalls of the insulating films is formed between electrodes of a highwithstand voltage and a low withstand voltage, namely, between the padregions PD2 of the peripheral circuit forming region 1A and the padregions PD2 of the transformer forming region 2A by combining theplurality of steps with each other, so that a high withstand-voltageregion and a low withstand-voltage region are separated from each other.This can gain a longer creepage distance, so that a high withstandvoltage electrically-insulated state can be achieved.

In addition, in the fourth embodiment, as shown in the peripheralcircuit forming region 1A in FIG. 40, the plurality of pad regions PD1are drawn out to the pad regions PD2 by means of the rewirings RW.Specifically, a plurality of source electrodes (or drain electrodes) ofMISFETs (NT, PT) are connected by the rewirings RW and drawn out to thepad regions PD2. This makes it possible to lower resistance as comparedwith the case where the pad regions PD1 are connected by the lower-layerwirings (M1 to M3) composed of Al or the like. That is, Cu thatconstitutes the rewirings RW has lower resistance than Al, and regardingthe rewirings RW located in the upper layer, wiring resistance can belowered because the wiring can be thickly formed. In addition, since thepad regions PD2 are disposed in the vicinity of the center of therewirings (strip-shaped straight line), as shown in FIG. 39, current canbe equally distributed (or collected) from the individual sourceelectrodes (or drain electrodes) of the MISFETs (NT, PT), so that theloads applied to the individual MISFETs can be more equalized.

Fifth Embodiment

The application field of the semiconductor devices described in thefirst to fourth embodiment is not limited, and the semiconductor devicesare widely applicable to devices that wirelessly transfer electricalsignals between two circuits the potentials of inputted electricalsignals of which are different from each other. Here, as an applieddevice, a three-phase motor will be described by way of example. FIG. 42is a diagram showing a circuit diagram of the three-phase motor in thefifth embodiment.

A motor M shown in FIG. 42 is a so-called three-phase motor, and hasinputs of a U phase, a V phase, and a W phase. In this circuit, variablespeed control of the number of revolutions of the motor M can beperformed by boosting input voltage from a power supply by means of abooster circuit BC, and performing conversion into alternate currenthaving a desired frequency by utilizing IGBT (Insulated Gate BipolarTransistor).

Each IGBT is connected to an IGBT driver, and controlled thereby. Inaddition, the IGBT driver is connected to a microcomputer MC viaisolators.

Here, in FIG. 42, the left side from the isolators, i.e., a side fromthe isolators to the microcomputer MC is a low-voltage region LC. Thatis, there is a circuit drivable at low voltage (for example, 50 V orless). On the other hand, in FIG. 42, the right side from the isolators,i.e., a side from the isolator to the motor M is a high-voltage regionHC. That is, there is a circuit driven at high voltage (for example, anAC RMS value of 100 Vrms or more).

In this manner, the transformers (inductors Ia, Ib, I1 to I4) describedin the first or second embodiment can be incorporated as isolatorsbetween the low-voltage region LC and the high-voltage region HC. Inparticular, according to the semiconductor devices of the first andsecond embodiment, in addition to the transformers (inductors Ia, Ib, I1to I4), various elements constituting peripheral circuits (for example,a MISFET) can be incorporated in the same chip or in a package.Therefore, for example, the isolators and the IGBT drivers shown in FIG.42 can be incorporated in the same chip or in the package. Of course, itis also possible to prepare a chip on the side of a low-voltage regionLC and another chip on the side of the high-voltage region HC, connectthese chips together via a transformer incorporated in either one of thechips, incorporate a microcomputer MC in the chip on the low-voltageregion LC, and incorporate a circuit driven at high voltage, such as anIGBT, in the chip on the high-voltage region HC.

The invention made by the present inventors has been specificallydescribed on the basis of embodiments thereof, but the present inventionis not limited to the embodiments described above, and obviously thepresent invention can be modified without departing from the gistthereof.

For example, the first-layer wirings M1 to the third-layer wirings M3are formed by patterning in the first embodiment, but the first-layerwirings M1 to the third-layer wirings M3 may be formed by means of aso-called “damascene process” of burying a conductive film in wiringtrenches provided in interlayer insulating films.

In addition, the insulating film between the inductors (Ia, Ib) iscomposed of the laminated film of polyimide films (PI1, PI2) in thefirst embodiment, but a different insulating film may be used. However,it is preferred that a polyimide film be used between the inductors (Ia,Ib) because of excellent withstand voltage thereof. In addition, sincethe polyimide film can be formed by application, and is also easy tophotosensitize, using a polyimide film makes it possible to form asemiconductor device by simple steps.

In addition, a laminated film of polyimide films (PI1, PI2) between theinductors (Ia, Ib) has a two-layered structure in the first embodiment,but more than two layers of polyimide films are laminated. In this case,individual polyimide films are laminated in a stairs-like shape (pyramidshape).

In addition, the ends of a laminated film of polyimide films (PI1, PI2)between the inductors (Ia, Ib) each have tapered shapes in the firstembodiment, but this is not a limitation. However, it is preferred thata side surface of each polyimide film have a tapered shape, i.e., anangle formed by a side surface of each polyimide film and the surface ofa substrate be set to 90° or less. Since the side surface of eachpolyimide film is formed in a tapered shape in this manner, peeling-offat the end of each polyimide film can be further reduced, and a stepdisconnection of a Cu seed layer (SE) can also be effectively reduced.

In addition, the SOI substrate has been described by way of example inthe first embodiment, but a so-called “bulk substrate” may be used.However, if a polyimide film is laminated above the SOI substrate, afilm stress of the polyimide film acts in a direction of relaxingwarpage of the SOI substrate. This improves the flatness of the SOIsubstrate, so that it is more effective that the semiconductor device ofthe first embodiment is applied to a semiconductor device using an SOIsubstrate.

What is claimed is:
 1. A semiconductor device comprising: asemiconductor substrate having a main surface; a first coil formed onthe main surface; a first insulating film formed over the first coil andhaving a first main surface; a second insulating film formed on thefirst main surface of the first insulating film and having a second mainsurface; and a second coil formed on the second main surface of thesecond insulating film, wherein the first main surface of the firstinsulating film has a first area on which the second insulating film isformed, and has a second area without the first area in a plan view, andwherein the second insulating film is surrounded by the second area inthe plan view.
 2. The semiconductor device according to claim 1, whereinthe first insulating film and the second insulating film compriseorganic insulating films.
 3. The semiconductor device according to claim1, further comprising: a third insulating film formed over the secondcoil, wherein the second main surface of the second insulating film hasa third area on which the third insulating film is formed and has afourth area without the third area in a plan view, and wherein the thirdinsulating film is surrounded with the fourth area in the plan view. 4.The semiconductor device according to claim 3, wherein the thirdinsulating film comprises an organic insulating film.
 5. Thesemiconductor device according to claim 1, further comprising: the mainsurface of the semiconductor having a fifth area on which the firstinsulating film is formed, a sixth area surrounding the fifth area, anda seventh area between the fifth area and the sixth area, and; a fourthinsulating film formed on the sixth area, wherein the first insulatingfilm is surrounding by the seventh area of the main surface of thesemiconductor substrate in the plan view, and wherein the firstinsulating film is surrounded by the fourth insulating film in the planview.
 6. The semiconductor device according to claim 5, wherein a grooveis formed between the second insulating film and the fourth insulatingfilm in a cross-sectional view, and wherein the second insulating filmis surrounded by the groove in the plan view.
 7. The semiconductordevice according to claim 1, wherein the second coil overlaps the firstcoil in the plan view.
 8. The semiconductor device according to claim 5,further comprising: a fifth insulating film formed between the mainsurface of the semiconductor substrate and the first insulating film ina cross-sectional view, wherein the first coil is covered with the fifthinsulating film in the cross-sectional view, and wherein the first andfourth insulating films are formed on the fifth insulating film in thecross-sectional view.
 9. The semiconductor device according to claim 8,wherein the fourth and fifth insulating films comprise organicinsulating films.
 10. The semiconductor device according to claim 5,further comprising: a first opening formed on a third insulating filmformed over the second coil, and a second opening formed on the fourthinsulating film, wherein a surface of a first electrode pad is exposedin the first opening, and wherein a surface of a second electrode pad isexposed in the second opening.